1. Field of the Invention
The present invention relates to a display apparatus used for a video phone, a video-conference and so on, and in particular, to the display apparatus having an image-taking function and a communication apparatus using this.
2. Description of Related Art
In display apparatuses used for a video phone, a video-conference (teleconference) and so on, there is one comprised of a camera which takes images of a user in order to display them on a display on the other side and a display which displays images of the other party taken on the other side so as to make a call while seeing the other party on the display.
Such a display apparatus is constituted so that the image of the other party displayed on the display gets to the user's eye level when seeing the other party on the display, and so it is possible to make a call as if seeing the other party in reality (refer to Japanese Patent Laid-Open Nos. 08-195945 and 01-286592 for instance).
FIG. 12 is a diagram describing a situation in which a conventional display apparatus for the video-conference is used, and FIG. 13 is a diagram describing an optical structure thereof.
In FIG. 12, reference numeral 1 denotes a flat-screen display to be connected to a personal computer (hereafter, referred to as a PC) not shown. Reference numeral 1a denotes a screen in which a face of the other party and documents used for conversation are displayed dividedly on the screen as required. Such a structure is implemented in an ordinary PC environment connected to a communication line such as the Internet.
Reference numeral 2 denotes a table. Reference numeral 3 denotes a video camera for transmitting the user's images to the other party, and includes an optical system shown in FIG. 13 built therein. The video camera 3 is not located between a face 4 and the screen 1a but is located below the screen 1a and out of a field of view when a person 4 sees the screen 1a. 
In FIG. 13, reference numeral 3a denotes an image-taking lens (it is comprised of multiple lenses in reality but is shown as one lens in FIG. 13 to simplify a description) built into the video camera 3, and 3b denotes an image-pickup element built into the video camera 3. Reference numeral 5 denotes the image of the person 4 on the image-pickup element 3b. 
In such a structure, a line A representing a virtual plane of the person 4 is projected like a plane C through the lens 3a. This is the “Scheimpflug rule” wherein, on specifying a place B vertical to an optical axis of the lens 3a, extensions of these axes A, B and C intersect at one point.
As for the image on the image-pickup element 3b obtained by such a structure, a image-taking magnification on a jaw side is high (due to a short distance) while the image-taking magnification on a crown side is low (long distance). This image is not so desirable.
Regarding the conventional example, however, there has been no proposal to keep a design intact and increase a resolution enough to determine a facial expression of the person as to a flat-screen display becoming mainstream among TV receivers and a thin-shaped display suited to portable telephones and mobile and personal computers.
As a first problem, an eye line of the person seeing the image on the display is approximately at a center of the display. To take an image of the eye line of the person, it is necessary to set a camera having the optical axis at the same location as the center of the same display, which is apt to reduce performance and a quality level as the display apparatus. An example of mounting the camera very close to the screen is thinkable in order to make up for that fault. In that case, however, the eye line cannot be caught inversely, or the face in the image looks as if seen obliquely.
As a second problem, the camera should be capable a focal length of a picture composition to take an image of some surrounding landscape centering on the person's face and having a resolution high enough to determine the facial expression of the person. If the optical system of such a image-taking magnification is built into a flat-screen display apparatus, however, its thickness increases and a precious design of the flat-screen display becomes reduced.
As a third problem, it is required to take an image of the user while seeing the facial expression of the other party (real-time property). In such cases, light for display is apt to become a ghost or a flare of an image-taking system and image quality may be degraded.